Solid Oxide Fuel Cell systems are high-efficiency generators of electric power from a variety of fuels including Natural Gas, Liquefied Petroleum Gas (LPG), Ethanol, and other hydrocarbon and non-hydrocarbon fuels. Due to the high operating temperature of an SOFC (700° C.-900° C.), the tail pipe exhaust is generally also at a high temperature. A known state-of-the-art integration of SOFC systems is as part of a Combined Heat and Power (CHP) system. Prior art CHP systems use the electrical output of the SOFC system directly, and also utilize the energy leaving the SOFC system in the form of hot exhaust for heating air or water for space heating or for heating water for domestic usage (showers, etc.). No fuel cell system is 100% efficient, so there will always be heat leaving in the SOFC exhaust. For a typical 1 kW electrical service demand (e.g., a small residence), the heating or thermal needs are typically in the range of 5-10 kW. If the SOFC system has a reasonably good electrical efficiency, for example 33%, the heat output for 1 kW net electric output is 2 kW. Since 2 kW is much less thermal energy than desired, auxiliary direct-fueled condensing or non-condensing burner-heat exchangers are commonly used to make up the difference. The best of these are 80-90% efficient in converting fuel to electric and thermal energy. In transportation (heavy-duty truck) applications, a direct fuel-fired heater is usually employed to provide heat to the sleeper cab. The fuel consumed for the fuel fired heater is used only for heating, and these units are typically 80-95% efficient.
Further, in many applications employing CHP systems for heating and power, it is desirable that air cooling (air conditioning) also be made available.
What is needed in the art is an improved CHP system with increased overall fuel efficiency that is capable of providing both heating and cooling.
It is a principal object of the present invention to increase the fuel efficiency of CHP systems while providing alternatively both heating and cooling of an effluent.